The present invention is directed to metal castings that include honeycomb structures. A honeycomb structure consists of a series of interconnected polygons. The honeycomb structure decreases the amount of metal alloy used to form the casting, and thereby reduces the weight of the casting. However, the decrease in the amount of material used does not unduly sacrifice the overall strength of the casting.
International Patent Application No. PCT/F19190/00157 concerns an aluminum door. The door is die-cast so that a honeycomb structure is situated between a bottom plate and a top plate. The average size of the diagonal of the spaces defining the honeycomb structure is 70 mm to about 150 mm. UK Patent Application No. GB 2 221 638 A also describes a structural component having a honeycomb structure. A model is produced that includes plural layers separated by spaces. The model is embedded in sand, and then molten metal is cast using the model. The metal casting has a honeycomb structure, but does not include a base plate or a top plate.
The processes that have been used to make honeycomb castings are limited in the structures that they can produce. The method described in International Application, PCT/F19190/00157, forms composites having both a base plate and a top plate. It currently is believed that it would be difficult, if not impossible, to form a honeycomb structure using this method wherein the honeycomb is open opposite a relatively thin base plate, such as less than about 5 mm thick. The process also could not form a honeycomb structure wherein the dimensions of the cells are small (such as less than about 40 mm) relative to the cells of the door. One reason for this is that it becomes increasingly difficult to pour the molten metal into the die and have the metal flow evenly through the die as the dimensions of the die decrease. Furthermore, it currently is believed that the method described in UK Patent Application No. GB 2 221 638 A cannot produce metal castings if any of the dimensions of the cells defining the honeycomb structure are smaller than about 5 mm (about 0.150 inch).
A need therefore exists for metal castings that include honeycomb structures which cannot be produced by previous prior-art processes. One example of such a casting is a honeycomb structure having relatively small cell dimensions, such as dimensions smaller than about 40 mm. A second example of such a casting is a honeycomb structure that is integrally cast with a base having a thickness of less than about 5 mm.